Systems for the remote sensing or remote locating of gases, in particular hydrocarbons such as methane, in the air or the atmosphere above the ground analyse light coming from the ground or the atmosphere as a result of radiation emission or scattering or reflection of light from a light source. To this end, the light beam is focused with a telescope onto a detector. The light beam may be a light beam in the ultraviolet, visible or infrared spectral range.
When high sensitivity is to be achieved and/or the amounts of light which are emitted by the atmosphere or a surface are relatively small, telescopes or receiving systems must be used with large optical apertures of several 10 cm in diameter.
If a surface is to be scanned quickly, either the receiving system has to be moved quickly or the field of view of the telescope must be continually realigned using a suitable device.
When receiving systems or telescopes with large optical apertures are used, it is not possible to move the receiving system or the telescope because of their size and the resultant drive problems.
With receiving systems with small optical apertures, i.e. with diameters of less than 1 cm, the use of deflection mirrors for deflecting the light beam between the surface or an object and the receiving system. The deflection mirrors are, for example, driven with piezo elements or galvo scanners. Such drive units are not available or are too complicated and expensive for receiving systems with larger optical apertures.
Furthermore, a deflection system with two deflection mirrors, the first deflection mirror deflecting the light beam by 90° is known from practice. A surface can be scanned relatively quickly using a second deflection mirror which deflects the light beam again. However, the use of two deflection mirrors is complicated design-wise and cost-intensive.
Furthermore, a cardan-driven deflection mirror is known. Here the deflection mirror is moved quickly around the cardanic axis. The very high accelerations which occur are a disadvantage. The fast reversal of movement puts very high mechanical strain on all components and very powerful drives are required for the deflection mirrors in order to achieve the required fast acceleration. Furthermore, the fast acceleration causes vibration in the measuring system which may have a disadvantageous effect.
Thus the object of the present invention is to create a device of the aforementioned type which has a simple design and can scan large surfaces quickly.